The present invention provides a process to produce isosorbide-containing polyesters. Said process allows for higher isosorbide incorporation than previously found while maintaining high polymeric molecular weights.
There is much interest in using polymeric components derived from biomass. The diol 1,4:3,6-dianhydro-D-sorbitol, hereinafter referred to as isosorbide, is readily made from renewable resources, such as sugars and starches. For example, isosorbide can be made from D-glucose by hydrogenation followed by acid-catalyzed dehydration. The preparation of isosorbide is known within the literature in, for example, G. Fleche, et. al., Starch/Starke, 38(1), pp. 26-30 (1986).
Isosorbide has been incorporated as a monomer into aliphatic and aromatic polyesters. A recent review is found in Hans R. Kricheldorf, et. al., J. M. S.-Rev. Macromol. Chem. Phys., C37(4), pp. 599-631 (1997). Homoaliphatic polyesters produced from isosorbide and aliphatic dicarboxylic acid chlorides were prepared by D. Braun, et. al., Die Angewandte Makromolekulare Chemie 199, pp. 191-201 (1992). The low molecular weight materials were utilized as polymeric plasticizers for PVC. Homopolyesters derived from isosorbide with adipoyl and succinoyl chloride are reported in Mustapha Majdoub, et. al., Eur. Polym. J., Vol. 30, No. 12, pp. 1431-1437 (1994). In a series of papers, Masahiko Okada, et. al., describe the synthesis and biodegradability of a series of aliphatic polyesters which incorporate isosorbide. The synthesis and biodegradability of poly(isosorbide succinate) derivatives was described in Masahiko Okada, et. al., Stud. Polym. Sci., (1994); Masahiko Okada, et. al., 12 (Biodegradable Plastics and Polymers), pp. 511-518. A series of aliphatic polyesters which incorporate isosorbide and their respective biodegradabilities was described in Masahiko Okada, et. al., Journal of Poly. Sci.: Part A: Polym. Chem., vol. 33, pp. 2813-2820 (1995); Masahiko Okada, et. al., J. Appl. Polym. Sci., 62(13), pp. 2257-2265 (1996); and Masahiko Okada, et. al., J. Appl. Polym. Sci., 77(2), pp. 338-346 (2000). In addition, copolymers of isosorbide with a mixture of aliphatic dicarboxylic acids and certain furan dicarboxylic acids are reported by Masahiko Okada, et. al., Journal of Polymer Science: Part A: Polymer Chemistry, Vol. 35, pp. 2729-2737 (1997); Masahiko Okada, et. al., Polym. Prepr. (Am. Chem. Soc., Div. Poly. Chem.) 39(20), pp. 152-153 (1998); and Masahiko Okada, et. al., J. Appl. Polym. Sci., 74(14), pp. 3342-3350 (1999).
Aromatic polyesters which incorporate isosorbide monomer units are also known. Mention is made again of Mustapha Majdoub, et. al., Eur. Polym. J., Vol. 30, No. 12, pp. 1431-1437 (1994), who describe homopolyesters derived from isosorbide and terephthaloyl chloride. See also, for example, R. Storbeck, et. al., Makromol. Chem., Vol. 194, pp. 53-64 (1993); R. Storbeck, et. al., Polymer, Vol. 34, p. 5003 (1993). However it is generally believed that secondary alcohols such as isosorbide have poor reactivity and are sensitive to acid-catalyzed reactions. See, for example, D. Braun, et. al., J. Prakt. Chem., Vol. 334, pp. 298-310 (1992). As a result of the poor reactivity, polyesters made with an isosorbide monomer and esters of terephthalic acid are expected to have a relatively low molecular weight. Ballauff, et. al., Polyesters (Derived from Renewable Sources), Polymeric Materials Encyclopedia, Vol. 8, p. 5892 (1996).
Copolymers containing isosorbide moieties, ethylene glycol moieties, and terephthaloyl moieties have been reported only rarely. A copolymer containing these three moieties, in which the mole ratio of ethylene glycol to isosorbide was about 90:10, was reported in published German Patent Application No. 1,263,981 (1968). The polymer was used as a minor component (about 10%) of a blend with polypropylene to improve the dyeability of polypropylene fiber. It was made by melt polymerization of dimethyl terephthalate, ethylene glycol, and isosorbide, but the conditions, which were described only in general terms in the publication, would not have given a polymer having a high molecular weight.
Copolymers of these same three monomers were described again recently, where it was observed that the glass transition temperature Tg of the copolymer increases with isosorbide monomer content up to about 200xc2x0 C. for the isosorbide terephthalate homopolymer. The polymer samples were made by reacting terephthaloyl dichloride in solution with the diol monomers. This method yielded a copolymer with a molecular weight that is apparently higher than was obtained in the German Patent Application described above but still relatively low when compared against other polyesters polymers and copolymers. Further, these polymers were made by a solution polymerization and were thus free of di(ethylene glycol) as a product of polymerization. See R. Storbeck, Dissertation, Universitat Karlsruhe (1994); R. Storbeck, et. al., J. Appl. Polymer Science, Vol. 59, pp. 1199-1202 (1996).
U.S. Pat. No. 4,418,174 describes a process for the preparation of polyesters useful as raw materials in the production of aqueous stoving laquers. The polyesters are prepared with an alcohol and an acid. One of the many preferred alcohols is dianhydrosorbitol. However, the average molecular weight of the polyesters is from 1,000 to 10,000 and no polyester actually containing a dianhydrosorbitol was made.
U.S. Pat. No. 5,179,143 describes a process for the preparation of compression molded materials. Also, described therein are hydroxyl containing polyesters. These hydroxyl containing polyesters are listed to include polyhydric alcohols, including 1,4:3,6-dianhydrosorbitol. Again, however, the highest molecular weights reported are relatively low, i.e.; 400 to 10,000, and no polyester actually containing the 1,4:3,6-dianhydrosorbitol moiety was made.
WO 97/14739 and WO 96/25449 describe cholesteric and nematic liquid crystalline polyesters that include isosorbide moieties as monomer units. Such polyesters have relatively low molecular weights and are not isotropic.
Recently, aromatic polyesters which incorporate isosorbide monomer units with relatively high molecular weights have been reported. Khanarian, et. al., in U.S. Pat. No. 5,958,581, describe polyester films which are produced from polyesters which incorporate terephthaloyl moieties, and optionally one or more other aromatic diacid moieties, ethylene glycol moieties, isosorbide moieties, and optionally one or more other diol moieties, said polyester having an inherent viscosity of at least 0.35 dL/g when measured as a 1% (weighvvolume) solution of the polyester in o-chlorophenol at a temperature of 25xc2x0 C.
Charbonneau, et. al., in U.S. Pat. No. 5,959,066, describe a method for producing a polyester comprising a terephthaloyl moiety; optionally, one or more other aromatic diacid moiety; and ethylene glycol moiety, and isosorbide moiety, and optionally one or more other diol moiety, such that the resultant polyester has an inherent viscosity of at least about 0.35.
Khanarian, et. al., in U.S. Pat. No. 6,025,061, describe a sheet comprising a polyester comprised of terephthaloyl moieties; optionally, one or more other aromatic diacid moieties; ethylene glycol moieties, isosorbide moieties, and optionally, one or more other diol moieties, such that said resultant polyester has an inherent viscosity of at least 0.35.
Charbonneau, et. al., in U.S. Pat. No. 6,063,464, describe a process to produce polyesters which incorporate isosorbide which have an inherent viscosity of at least 0.35 dL/g when measured as a 1% (weight/volume) solution of the polyester in o-chlorophenol at a temperature of 25xc2x0 C. They generally teach the use of aromatic and alicyclic diacids. A shortcoming found within this disclosure was the low incorporation rate of the isosorbide monomer. Of the 16 preparative examples included within this disclosure where the percentage of incorporated isosorbide into the polymer could be assessed, the incorporation level of added isosorbide monomer into the as produced polymer ranged from 12 to 70 percent. The average incorporation rate of added isosorbide monomer into the as made polymer was disclosed to be 48 percent. This inefficiency of isosorbide monomer incorporation into the polymer may lead to complex glycol recovery and separation processes.
Charbonneau, et. al., in U.S. Pat. No. 6,063,465, describe a polyester container made from a polyester having ethylene glycol moieties, isosorbide moieties, and terephthaloyl moieties.
Charbonneau, et. al., in U.S. Pat. No. 6,063,495, describe a polyester fiber made from a polyester containing ethylene glycol moieties, isosorbide moieties, and terephthaloyl moieties.
Khanarian, et. al., in U.S. Pat. No. 6,126,992, describe optical articles produced from certain isosorbide-containing transparent polyesters.
The polyester production process of the present invention provides for a higher isosorbide monomer incorporation rate than has been found in the art while maintaining good polymeric molecular weights.
The current invention is a process to produce polyesters which incorporate isosorbide. The polyesters produced are comprised essentially of 45 to 50 mole percent of a dicarboxylic acid component, 0.1 to 40 mole percent isosorbide, 10 to 49.9 mole percent of a diol component other than ethylene glycol or di(ethylene glycol), and 0 to 5.0 mole percent of a polyfunctional branching agent component.
The process comprises: melt mixing a first polyester which incorporates isosorbide comprised essentially of: 45.0 to 50.0 mole percent of a dicarboxylic acid component; 5.0 to 50.0 mole percent of isosorbide; 0 to 45.0 mole percent of a diol component other than ethylene glycol or di(ethylene glycol); and 0 to 5.0 mole percent of a polyfunctional branching agent component; with a second polyester comprised essentially of: 45.0 to 50.0 mole percent of a dicarboxylic acid component, 45.0-50.0 mole percent of a diol component other than isosorbide; and 0 to 5.0 mole percent of a polyfunctional branching agent component; at a temperature and for a time sufficient to effect transesterification, optionally followed by a finishing process.